The most common fingerprinting techniques involve the use of fingerprint dusting powders such as graphite powder or zinc powder etc., which is dusted on to the suspect surface using a brush. The powder adheres to any deposits of skin secretions which if resulting from a fingerprint will be in the form of a unique pattern. The powdered representation so obtained can be subsequently lifted by applying to it the sticky side of an adhesive-backed transparent sheet which allows the powdered representation of the print to be lifted for further examination for example at a forensic laboratory and can subsequently be used as evidence in a court of law.
One of the disadvantages of this method is that fingerprints which are more than a few hours old cease to respond to powder treatment. It is believed that the secretions from the skin which adhere to the surface of the member on which the finger or thumb has been placed dry up or otherwise react with the surface or the atmosphere and once this so-called drying up process has been completed there has hitherto been no method of obtaining from the surface any information relating to the fingerprint.
Another disadvantage is that the dusting/powder method cannot be used on certain materials such as polythene and similar plastic sheet materials which apparently exhibit an attraction or stickiness which overrides the secretions from a fingerprint and render it virtually impossible to detect a fingerprint on such a surface. This is of significance in drug offences since most drugs are contained in polythene bags and the use of conventional powder dusting techniques for fingerprinting the drug bags have proved totally ineffective.
It is also a disadvantage of the known method (i.e. the so-called dusting technique) that the method is ineffective for removing fingerprints from the human skin. Were it to be possible to obtain fingerprint information from the skin of rape cases, assult cases and the like, additional very strong evidence could be adduced in such cases for ensuring that only the guilty person was convicted.